1. Field of the Invention
This invention relates to valves and valve devices for automatically closing a valve to stop the flow of a fluid in a conduit when the device is subjected to shock and vibration forces such as experienced during an earthquake. The improved shock sensor and actuation device uses gravity to aid in activating a valve closure mechanism.
2. Description of the Prior Art
Various mechanisms to sense shock and vibration to activate the closing of a valve exist in the art. Such shock actuated valves generally are inserted in a fluid flow line, have a rotating valve element for opening and closing the fluid flow line, and have a mechanism to maintain an open valve position until such time as a shock or vibration of specified characteristics is sensed by a device which then causes the valve to close.
The present invention relates to shutoff valves which use a weight in the form of a ball to sense shock or vibration which force displaces the ball from a normal rest location to actuate a mechanism to cause a valve to close. Reference to U.S. Pat. No. 4,915,122 issued Apr. 10, 1990 shows a shock actuated valve which uses a ball motion to actuate a valve due to earthquake forces and similar shock forces. The improved device modifies the pedestal on which the ball rests to allow gravity force to act on the ball once it has been moved from its position of rest to aid in the actuation of the shock actuation control mechanism. The modification of adding a step to the pedestal upper perimeter surface improves the accuracy for the elapsed time for the valve to be actuated once a specified force has been sensed. In previous art mechanisms the ball motion may be compounded by the ball not initially actuating the shock actuation control mechanism due to for example the ball moving, but rebounding or retreating from an initially urged position to be moved to a second position by the forces. These non-actuating motions of the ball delay valve closure which may increase the possibility of damage as for examples during an earthquake.
It is desirable to provide a vertical shock responsive fluid valve assembly with the capability of automatically closing a fluid valve in response to earthquake forces or other shock forces of a predetermined magnitude.